1. Field of Invention
The present invention relates to a channel buffering method of Internet protocol television (IPTV). More particularly, the present invention relates to a channel buffering method for dynamically altering number of IPTV channels through two trimming numerical values.
2. Related Art
The IPTV is a service that broadcasts multiple TV channels to the digital television through an IP (Internet Protocol) network. In the present invention, the term of digital television is used to represent any equipment or equipment assembly that is capable to receive digital channels and displayed them on the TV screen, such as a digital TV or an assembly of a set-top box (STB) with a TV set. The largest difference between the IPTV and the current wireless/cable television lies in that, the wireless/cable television transports all the channels, but the IPTV only transfers a limited number of channels to the digital television. Therefore, when the user selects his or her favorite channel from all the channels provided by the IPTV headend, the IPTV headend would only transfer the selected channel to the digital television in the user's house. In this way, the user will not encounter unselected channels, so as to save the bandwidth occupied for transmitting the unselected channels over the network.
When the user switches the TV channel, the digital television sends a request for receiving the new channel. Once the IPTV headend receives the request for receiving the new channel, it delivers the new channel to the digital television over Internet. A zap time refers to the time duration from sending the request by the digital television to receiving the new channel. For the user's point of view, if the zap time is shorter, he or she spends less time for switching to the new channel. Statistics shows that, the user may feel uncomfortable after waiting for longer than 1.5 seconds. Therefore, in order to avoid the situation that the user may feel the time waiting for switching to the new channel is too long, some manufacturers begin to think about how to shorten the zap time. Currently, a process of shortening the zap time is proposed, in which a plurality of channels is buffered on a home gateway (HG) 112. The digital television 111 is connected with the HG 112, and the HG 112 communicates with the IPTV headend 123 over the access network 120 (i.e., Internet herein), as shown in FIG. 1. If the user switches the channel to a channel buffered in the HG 112, the HG 112 directly delivers the channel to the digital television 111, without requiring the IPTV headend 123 for redelivery, such that the time for delivering the channel from the IPTV headend 123 to the HG 112 is omitted from the zap time.
Buffering the channel in the HG 112 can shorten the zap time, so it is very important whether the channel switched by the user is buffered on the HG 112. However, in the current solution of HG 112, the numbers of forward and backward buffered channel are fixed. The function of dynamically adjusting the size of the buffered channel section does not exist. That is to say, when the user switches the channel quickly, due to the excessive long delay time for delivering the channel over the access network (Internet) 120, the HG 112 generally cannot receive the user's desirable channels on time, which means the delay time for the channel switching is too long. Therefore, how to provide a method of dynamically adjusting the number of channel buffering so that the channel can be buffered before user quickly switches to it is still an urgent problem to be solved by the IPTV service providers and the users.